1. Field of the Invention
The present invention relates to an adhesive film for manufacturing a semiconductor device, and a method for manufacturing a semiconductor device.
2. Discussion of the Related Art
In recent years, CSP (Chip Size/Scale Package) technique has been remarked in LSI (Large Scale IC) mounting technology. In CSP technique, a package having lead terminals inside thereof, as represented by a QFN (Quad Flat Non-leaded package), is one of package forms that are especially remarked, from the viewpoint of miniaturization and high integration. Among the methods for manufacturing QFN described above, recently, there has especially been remarked a method for dramatically improving productivity per area of a lead frame, by systematically arranging plural chips for a QFN on die pads in package pattern regions of a lead frame, simultaneously encapsulating with an encapsulation resin in cavities of a mold, and thereafter cutting the lead frame into individual QFN structures by dicing.
In the method for manufacturing QFN in which plural semiconductor chips are simultaneously encapsulated, an outer side of a resin encapsulation region extending outwardly from the package pattern region is only clamped by the mold die during the resin encapsulation. Therefore, in the package pattern region, especially in the central portion thereof, since the outer lead surface cannot be pressed with a sufficient pressure to the mold die, it is very difficult to prevent leakage of the encapsulation resin to the outer lead side, and as a result, a problem of coating the terminals of the QFN with the resin is likely to be caused.
In view of the above, in the method for manufacturing a QFN, there has been proposed a method for preventing leakage of an encapsulation resin to an outer side, comprising adhering an adhesive tape to an outer pad surface of the lead frame, thereby giving a sealing effect by masking the outer pad surface of the lead frame with the adhesive tape (see Japanese Patent Laid-Open No. 2000-294580). In this method, the adhesive tape is adhered together to the outer pad surface of the lead frame in the beginning of the manufacturing steps, and thereafter being adhered together during a semiconductor chip mounting step, and a wire bonding step, up to an encapsulating step with an encapsulation resin.
Further, in recent years, there has also been proposed a method for manufacturing a so-called leadless semiconductor device in which the semiconductor is formed by adhering together a copper foil to a backing and etching the conductor (see Japanese Patent Laid-Open No. Hei 9-252014) for the purpose of further thinning of the semiconductor device. According to this method, since the conductor is formed on a backing, the conductor can be made thinner. Also, there is little abrasion of a blade during dicing, since it is not necessary to cut the lead frame when obtaining individual semiconductor devices molded with an encapsulation resin.
It is necessary that the adhesive tape and the backing to be used in the above-mentioned methods not only prevent leakage of an encapsulation resin but also have properties which meet the requirement, such as having high heat resistance sufficient to withstand high temperatures in a semiconductor chip mounting step; not interfering with delicate operability in the wire bonding step; and allowing the adhesive to be well stripped away without remaining on an adherend after the termination of the encapsulation step.
In view of the above, in the method for manufacturing a semiconductor device, a silicone-based adhesive having excellent heat resistance and appropriate elastic modulus and adhesive strength has been generally used in the adhesive layer of the adhesive film which is to be finally stripped away.
However, since the silicone-based adhesive used in a heat-resistant adhesive tape is cross-linked in a high degree for the purpose of increasing heat resistance, the adhesive has a high elastic modulus and poor fluidity. Therefore, in the case of manufacturing a semiconductor device having a so-called standoff wherein a part of a conductor projects from an encapsulation resin, the silicone-based adhesive has a disadvantage that it is difficult to allow a part of the conductor to be embedded in the adhesive layer in the manufacturing step.
An object of the present invention is to provide an adhesive film for manufacturing a semiconductor device which is to be finally removed in the method, which can be suitably used in the manufacture of a semiconductor device having a so-called standoff wherein a part of a conductor projects from an encapsulation resin.
These and other objects of the present invention will be apparent from the following description.